1. Field of the Invention
The present invention relates generally to the field of semiconductor memory devices. More particularly, the present invention relates to an improved resistive random access memory (RRAM) device, which utilizes spacer-type resistance layer and top electrode and has a cell size of 2 F2. A method of fabricating such RRAM device is also disclosed.
2. Description of the Prior Art
Resistive switching random access memory or RRAM devices have certain beneficial characteristics over other types of memory devices, such as low power consumption, high speed, excellent bit resolution, high degree of scaling of miniaturization, non-volatile, and low cost, and therefore have become a promising next-generation non-volatile memory to replace flash memory.
RRAM may be characterized by a resistor or a resistance layer disposed between a top electrode and a bottom electrode of a storage node, which may be fabricated in a semiconductor pillar structure and stacked with a diode. The resistor may have a current-voltage characteristic which may be varied according to an applied voltage. Once the current-voltage characteristic is varied, the varied current-voltage characteristic of the resistor may be maintained until a reset voltage is applied to the resistor. RRAM devices store data by varying the resistance of the resistor between a high resistance state (HRS) and a low resistance state (LRS), arguably due to the formation/collapse of conduction filaments in the resistance layer. Data may be written to a selected RRAM device by applying a predetermined voltage, at a predetermined polarity, for a predetermined duration. To ensure the stability when operating the RRAM device, it is believed that maintaining a certain amount of the conduction filaments is essential.
It is also believed that, when the RRAM device is operated, the quantity of conduction filaments is proportional to the contact area between the resistance layer and the electrode. As the size of the memory cell shrinks, however, the variation or deviation of the quantity of conduction filaments created during the operation of the RRAM device becomes critical and may significantly influence the device reliability. Accordingly, there is a need in this industry to provide an improved RRAM structure and fabrication method thereof to solve the above-mentioned problems or shortcomings.